Method and device for applying value on basis of coverage extension level

ABSTRACT

A method performed by a wireless device in a wireless communication system includes receiving multiple thresholds from a base station (BS); measuring a quality of a cell; determining a coverage enhancement (CE) level of the wireless device based on the multiple thresholds and the measured quality of the cell; receiving random access channel (RACH) information including at least one window size value and at least one timer value for contention resolution, from the BS; selecting a window size value and a timer value among the RACH information based on the determined CE level; transmitting a first message for the RACH to the BS; receiving a second message for the RACH based on the selected window size value, from the BS; and starting a timer for contention resolution based on the selected timer value regarding a third message for the RACH. Further, the CE level is determined as a CE level 0, when the measured quality is above or equal to all of the multiple thresholds.

CROSS-REFERENCE TO RELATED APPLICATIONS

This Application is a Continuation of co-pending U.S. patent applicationSer. No. 15/562,700 filed on Sep. 28, 2017, which is the National Phaseof PCT International Application No. PCT/KR2016/003570 filed on Apr. 6,2016, which claims the priority benefit under 35 U.S.C. § 119(e) to U.S.Provisional Application Nos. 62/144,338 filed on Apr. 8, 2015 and62/143,819 filed on Apr. 7, 2015, all of which are hereby expresslyincorporated by reference into the present application.

BACKGROUND OF THE INVENTION Field of the Invention

The present invention relates to a wireless communication system, andmore particularly, to a method of applying a value corresponding to acoverage extension level on the basis of the coverage extension level,and an apparatus supporting the method.

Discussion of the Related Art

3GPP (3rd Generation Partnership Project) LTE (Long Term Evolution) thatis an advancement of UMTS (Universal Mobile Telecommunication System) isbeing introduced with 3GPP release 8. In 3GPP LTE, OFDMA (orthogonalfrequency division multiple access) is used for downlink, and SC-FDMA(single carrier-frequency division multiple access) is used for uplink.The 3GPP LTE adopts MIMO (multiple input multiple output) having maximumfour antennas. Recently, a discussion of 3GPP LTE-A (LTE-Advanced) whichis the evolution of the 3GPP LTE is in progress.

In recent years, machine-to-machine/Internet of Things (M2M/IoT), whichconnects all every objects through networks to facilitate obtaining andtransmitting necessary information anytime and anywhere, thereby makingit possible to offer and use various services, has become a major issuefor a next-generation communication market.

While early M2M started with a sensor and an RFID network mainly forlocal areas, various wired/wireless networks may be used with graduallydiversifying purposes and characteristics of applications. Recently, M2Mbased on a mobile communication network receives growing attention inview of the mobility of objects, a wide range of service areas includingnot only islands and mountains but also the sea, ease of networkmanagement and maintenance, security for reliable data transmission, andguarantee of service quality. Accordingly, with studies on thefeasibility of M2M started in 2005, the 3GPP has been conducting afull-scale standardization project under the name “Machine TypeCommunications (MTC)” since 2008.

The 3GPP regards a machine as an entity that does not require directhuman manipulation or intervention and defines MTC as a form of datacommunication involving one or more of machines. Typical examples of themachine include a smart meter and a vending machine that are equippedwith a mobile communication module. Recently, with the introduction of asmart phone that performs communication by automatically connecting to anetwork, without any user operation or intervention, depending on auser's location or conditions, a mobile terminal having an MTC functionis considered as a form of a machine. Also, a gateway-type MTC deviceconnected to an IEEE 802.15 WPAN-based subminiature sensor or RFID isalso considered.

SUMMARY OF THE INVENTION

In case of a UE operating in a coverage extension mode, the higher thecoverage extension level, the greater the number of repetitions requiredfor reception, or the longer the time required for successfultransmission/reception. For example, the higher the coverage extensionlevel of the UE, the longer the timer value and the greater the windowsize. Accordingly, the present invention proposes a method in which theUE applies a value corresponding to the coverage extension level on thebasis of the coverage extension level, and an apparatus supporting themethod.

According to one embodiment, there is provided a method by which a UEapplies a value corresponding to a coverage enhancement (CE) level onthe basis of the CE level in a wireless communication system. The methodmay include: receiving from a network a list including one or morevalues corresponding to one or more CE levels; determining the CE level;and applying a value corresponding to the determined CE level among thevalues included in the list.

The list may include a parameter used in a random access procedure. Theparameter used in the random access procedure may include at least anyone of mac-ContentionResolutionTimer, ra-ResponseWindowSize, andpreambleTransMax.

The method may further include performing a cell attach procedure, acell re-attach procedure, a random access procedure, or datatransmission/reception by using a value corresponding to the applied CElevel.

The list may include one or more timer values corresponding to the oneor more CE levels. The timer value may be at least any one of T300,T303, T305, T306, and a timer value used by the UE to declare a failurein SIB acquisition. The timer value may bemac-ContentionResolutionTimer. The higher the CE level, the longer thetimer value.

The list may include one or more window sizes corresponding to the oneor more CE levels. The window size may be ra-ResponseWindowSize.

The list may include one or more maximum counter values corresponding tothe one or more CE levels. The maximum counter value may beconnEstFailCount or preambleTransMax.

The UE may be in an RRC_IDLE state.

According to another embodiment, there is provided a method by which aUE applies a value corresponding to a CE level on the basis of the CElevel in a wireless communication system. The method may include:receiving from a network a specific value and one or more offset valuescorresponding to one or more CE levels; determining the CE level;manipulating the specific value by using an offset value correspondingto the determined CE level; and applying the manipulated specific value.

According to another embodiment, there is provided a UE which applies avalue corresponding to a CE level on the basis of the CE level in awireless communication system. The UE may include: a memory; atransceiver; and a processor operatively coupled to the memory and thetransceiver. The processor may be configured for: controlling thetransceiver to receive from a network a list including one or morevalues corresponding to one or more CE levels; determining the CE level;and applying a value corresponding to the determined CE level among thevalues included in the list.

Smooth communication of a UE operating in a coverage extension mode canbe supported by varying a value applied depending on the coverageextension level of the UE.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows LTE system architecture.

FIG. 2 shows a control plane of a radio interface protocol of an LTEsystem.

FIG. 3 shows a user plane of a radio interface protocol of an LTEsystem.

FIG. 4 shows a procedure in which UE that is initially powered onexperiences a cell selection process, registers it with a network, andthen performs cell reselection if necessary.

FIG. 5 shows an RRC connection establishment procedure.

FIG. 6 shows an RRC connection reconfiguration procedure.

FIG. 7 shows an RRC connection re-establishment procedure.

FIG. 8 shows an example of MTC.

FIG. 9 shows an example of cell coverage enhancement for an MTC device.

FIG. 10 shows a method of considering a CE level of a UE in acontention-based random access procedure according to an embodiment ofthe present invention.

FIG. 11 shows a method of considering a CE level of a UE in an RRCconnection establishment procedure according to an embodiment of thepresent invention.

FIG. 12 shows a method of considering a CE level of a UE in an RRCconnection establishment procedure according to an embodiment of thepresent invention.

FIG. 13 is a flowchart illustrating a method of applying a valuecorresponding to a CE level on the basis of the CE level of a UEaccording to an embodiment of the present invention.

FIG. 14 is a flowchart illustrating a method of applying a valuecorresponding to a CE level on the basis of the CE level of a UEaccording to an embodiment of the present invention.

FIG. 15 is a block diagram illustrating a wireless communication systemaccording to the embodiment of the present invention.

DETAILED DESCRIPTION OF THE EMBODIMENTS

The technology described below can be used in various wirelesscommunication systems such as code division multiple access (CDMA),frequency division multiple access (FDMA), time division multiple access(TDMA), orthogonal frequency division multiple access (OFDMA), singlecarrier frequency division multiple access (SC-FDMA), etc. The CDMA canbe implemented with a radio technology such as universal terrestrialradio access (UTRA) or CDMA-2000. The TDMA can be implemented with aradio technology such as global system for mobile communications(GSM)/general packet ratio service (GPRS)/enhanced data rate for GSMevolution (EDGE). The OFDMA can be implemented with a radio technologysuch as institute of electrical and electronics engineers (IEEE) 802.11(Wi-Fi), IEEE 802.16 (WiMAX), IEEE 802.20, evolved UTRA (E-UTRA), etc.IEEE 802.16m is evolved from IEEE 802.16e, and provides backwardcompatibility with a system based on the IEEE 802.16e. The UTRA is apart of a universal mobile telecommunication system (UMTS). 3rdgeneration partnership project (3GPP) long term evolution (LTE) is apart of an evolved UMTS (E-UMTS) using the E-UTRA. The 3GPP LTE uses theOFDMA in a downlink and uses the SC-FDMA in an uplink. LTE-advanced(LTE-A) is an evolution of the LTE.

For clarity, the following description will focus on LTE-A. However,technical features of the present invention are not limited thereto.

FIG. 1 shows LTE system architecture. The communication network iswidely deployed to provide a variety of communication services such asvoice over internet protocol (VoIP) through IMS and packet data.

Referring to FIG. 1, the LTE system architecture includes one or moreuser equipment (UE; 10), an evolved-UMTS terrestrial radio accessnetwork (E-UTRAN) and an evolved packet core (EPC). The UE 10 refers toa communication equipment carried by a user. The UE 10 may be fixed ormobile, and may be referred to as another terminology, such as a mobilestation (MS), a user terminal (UT), a subscriber station (SS), awireless device, etc.

The E-UTRAN includes one or more evolved node-B (eNB) 20, and aplurality of UEs may be located in one cell. The eNB 20 provides an endpoint of a control plane and a user plane to the UE 10. The eNB 20 isgenerally a fixed station that communicates with the UE 10 and may bereferred to as another terminology, such as a base station (BS), a basetransceiver system (BTS), an access point, etc. One eNB 20 may bedeployed per cell. There are one or more cells within the coverage ofthe eNB 20. A single cell is configured to have one of bandwidthsselected from 1.25, 2.5, 5, 10, and 20 MHz, etc., and provides downlinkor uplink transmission services to several UEs. In this case, differentcells can be configured to provide different bandwidths.

Hereinafter, a downlink (DL) denotes communication from the eNB 20 tothe UE 10, and an uplink (UL) denotes communication from the UE 10 tothe eNB 20. In the DL, a transmitter may be a part of the eNB 20, and areceiver may be a part of the UE 10. In the UL, the transmitter may be apart of the UE 10, and the receiver may be a part of the eNB 20.

The EPC includes a mobility management entity (MME) which is in chargeof control plane functions, and a system architecture evolution (SAE)gateway (S-GW) which is in charge of user plane functions. The MME/S-GW30 may be positioned at the end of the network and connected to anexternal network. The MME has UE access information or UE capabilityinformation, and such information may be primarily used in UE mobilitymanagement. The S-GW is a gateway of which an endpoint is an E-UTRAN.The MME/S-GW 30 provides an end point of a session and mobilitymanagement function for the UE 10. The EPC may further include a packetdata network (PDN) gateway (PDN-GW). The PDN-GW is a gateway of which anendpoint is a PDN.

The MME provides various functions including non-access stratum (NAS)signaling to eNBs 20, NAS signaling security, access stratum (AS)security control, Inter core network (CN) node signaling for mobilitybetween 3GPP access networks, idle mode UE reachability (includingcontrol and execution of paging retransmission), tracking area listmanagement (for UE in idle and active mode), P-GW and S-GW selection,MME selection for handovers with MME change, serving GPRS support node(SGSN) selection for handovers to 2G or 3G 3GPP access networks,roaming, authentication, bearer management functions including dedicatedbearer establishment, support for public warning system (PWS) (whichincludes earthquake and tsunami warning system (ETWS) and commercialmobile alert system (CMAS)) message transmission. The S-GW host providesassorted functions including per-user based packet filtering (by e.g.,deep packet inspection), lawful interception, UE Internet protocol (IP)address allocation, transport level packet marking in the DL, UL and DLservice level charging, gating and rate enforcement, DL rate enforcementbased on APN-AMBR. For clarity MME/S-GW 30 will be referred to hereinsimply as a “gateway,” but it is understood that this entity includesboth the MME and S-GW.

Interfaces for transmitting user traffic or control traffic may be used.The UE 10 and the eNB 20 are connected by means of a Uu interface. TheeNBs 20 are interconnected by means of an X2 interface. Neighboring eNBsmay have a meshed network structure that has the X2 interface. The eNBs20 are connected to the EPC by means of an S1 interface. The eNBs 20 areconnected to the MME by means of an S1-MME interface, and are connectedto the S-GW by means of S1-U interface. The S1 interface supports amany-to-many relation between the eNB 20 and the MME/S-GW.

The eNB 20 may perform functions of selection for gateway 30, routingtoward the gateway 30 during a radio resource control (RRC) activation,scheduling and transmitting of paging messages, scheduling andtransmitting of broadcast channel (BCH) information, dynamic allocationof resources to the UEs 10 in both UL and DL, configuration andprovisioning of eNB measurements, radio bearer control, radio admissioncontrol (RAC), and connection mobility control in LTE_ACTIVE state. Inthe EPC, and as noted above, gateway 30 may perform functions of pagingorigination, LTE_IDLE state management, ciphering of the user plane, SAEbearer control, and ciphering and integrity protection of NAS signaling.

FIG. 2 shows a control plane of a radio interface protocol of an LTEsystem. FIG. 3 shows a user plane of a radio interface protocol of anLTE system.

Layers of a radio interface protocol between the UE and the E-UTRAN maybe classified into a first layer (L1), a second layer (L2), and a thirdlayer (L3) based on the lower three layers of the open systeminterconnection (OSI) model that is well-known in the communicationsystem. The radio interface protocol between the UE and the E-UTRAN maybe horizontally divided into a physical layer, a data link layer, and anetwork layer, and may be vertically divided into a control plane(C-plane) which is a protocol stack for control signal transmission anda user plane (U-plane) which is a protocol stack for data informationtransmission. The layers of the radio interface protocol exist in pairsat the UE and the E-UTRAN, and are in charge of data transmission of theUu interface.

A physical (PHY) layer belongs to the L1. The PHY layer provides ahigher layer with an information transfer service through a physicalchannel. The PHY layer is connected to a medium access control (MAC)layer, which is a higher layer of the PHY layer, through a transportchannel. A physical channel is mapped to the transport channel. Data istransferred between the MAC layer and the PHY layer through thetransport channel. Between different PHY layers, i.e., a PHY layer of atransmitter and a PHY layer of a receiver, data is transferred throughthe physical channel using radio resources. The physical channel ismodulated using an orthogonal frequency division multiplexing (OFDM)scheme, and utilizes time and frequency as a radio resource.

The PHY layer uses several physical control channels. A physicaldownlink control channel (PDCCH) reports to a UE about resourceallocation of a paging channel (PCH) and a downlink shared channel(DL-SCH), and hybrid automatic repeat request (HARQ) information relatedto the DL-SCH. The PDCCH may carry a UL grant for reporting to the UEabout resource allocation of UL transmission. A physical control formatindicator channel (PCFICH) reports the number of OFDM symbols used forPDCCHs to the UE, and is transmitted in every subframe. A physicalhybrid ARQ indicator channel (PHICH) carries an HARQ acknowledgement(ACK)/non-acknowledgement (NACK) signal in response to UL transmission.A physical uplink control channel (PUCCH) carries UL control informationsuch as HARQ ACK/NACK for DL transmission, scheduling request, and CQI.A physical uplink shared channel (PUSCH) carries a UL-uplink sharedchannel (SCH).

A physical channel consists of a plurality of subframes in time domainand a plurality of subcarriers in frequency domain. One subframeconsists of a plurality of symbols in the time domain. One subframeconsists of a plurality of resource blocks (RBs). One RB consists of aplurality of symbols and a plurality of subcarriers. In addition, eachsubframe may use specific subcarriers of specific symbols of acorresponding subframe for a PDCCH. For example, a first symbol of thesubframe may be used for the PDCCH. The PDCCH carries dynamic allocatedresources, such as a physical resource block (PRB) and modulation andcoding scheme (MCS). A transmission time interval (TTI) which is a unittime for data transmission may be equal to a length of one subframe. Thelength of one subframe may be 1 ms.

The transport channel is classified into a common transport channel anda dedicated transport channel according to whether the channel is sharedor not. A DL transport channel for transmitting data from the network tothe UE includes a broadcast channel (BCH) for transmitting systeminformation, a paging channel (PCH) for transmitting a paging message, aDL-SCH for transmitting user traffic or control signals, etc. The DL-SCHsupports HARQ, dynamic link adaptation by varying the modulation, codingand transmit power, and both dynamic and semi-static resourceallocation. The DL-SCH also may enable broadcast in the entire cell andthe use of beamforming. The system information carries one or moresystem information blocks. All system information blocks may betransmitted with the same periodicity. Traffic or control signals of amultimedia broadcast/multicast service (MBMS) may be transmitted throughthe DL-SCH or a multicast channel (MCH).

A UL transport channel for transmitting data from the UE to the networkincludes a random access channel (RACH) for transmitting an initialcontrol message, a UL-SCH for transmitting user traffic or controlsignals, etc. The UL-SCH supports HARQ and dynamic link adaptation byvarying the transmit power and potentially modulation and coding. TheUL-SCH also may enable the use of beamforming. The RACH is normally usedfor initial access to a cell.

A MAC layer belongs to the L2. The MAC layer provides services to aradio link control (RLC) layer, which is a higher layer of the MAClayer, via a logical channel. The MAC layer provides a function ofmapping multiple logical channels to multiple transport channels. TheMAC layer also provides a function of logical channel multiplexing bymapping multiple logical channels to a single transport channel. A MACsublayer provides data transfer services on logical channels.

The logical channels are classified into control channels fortransferring control plane information and traffic channels fortransferring user plane information, according to a type of transmittedinformation. That is, a set of logical channel types is defined fordifferent data transfer services offered by the MAC layer. The logicalchannels are located above the transport channel, and are mapped to thetransport channels.

The control channels are used for transfer of control plane informationonly. The control channels provided by the MAC layer include a broadcastcontrol channel (BCCH), a paging control channel (PCCH), a commoncontrol channel (CCCH), a multicast control channel (MCCH) and adedicated control channel (DCCH). The BCCH is a downlink channel forbroadcasting system control information. The PCCH is a downlink channelthat transfers paging information and is used when the network does notknow the location cell of a UE.

The CCCH is used by UEs having no RRC connection with the network. TheMCCH is a point-to-multipoint downlink channel used for transmittingMBMS control information from the network to a UE. The DCCH is apoint-to-point bi-directional channel used by UEs having an RRCconnection that transmits dedicated control information between a UE andthe network.

Traffic channels are used for the transfer of user plane informationonly. The traffic channels provided by the MAC layer include a dedicatedtraffic channel (DTCH) and a multicast traffic channel (MTCH). The DTCHis a point-to-point channel, dedicated to one UE for the transfer ofuser information and can exist in both uplink and downlink. The MTCH isa point-to-multipoint downlink channel for transmitting traffic datafrom the network to the UE.

Uplink connections between logical channels and transport channelsinclude the DCCH that can be mapped to the UL-SCH, the DTCH that can bemapped to the UL-SCH and the CCCH that can be mapped to the UL-SCH.Downlink connections between logical channels and transport channelsinclude the BCCH that can be mapped to the BCH or DL-SCH, the PCCH thatcan be mapped to the PCH, the DCCH that can be mapped to the DL-SCH, andthe DTCH that can be mapped to the DL-SCH, the MCCH that can be mappedto the MCH, and the MTCH that can be mapped to the MCH.

An RLC layer belongs to the L2. The RLC layer provides a function ofmanipulating a size of data, so as to be suitable for a lower layer totransmit the data, by concatenating and segmenting the data receivedfrom an upper layer in a radio section. In addition, to ensure a varietyof quality of service (QoS) required by a radio bearer (RB), the RLClayer provides three operation modes, i.e., a transparent mode (TM), anunacknowledged mode (UM), and an acknowledged mode (AM). The AM RLCprovides a retransmission function through an automatic repeat request(ARQ) for reliable data transmission. Meanwhile, a function of the RLClayer may be implemented with a functional block inside the MAC layer.In this case, the RLC layer may not exist.

A packet data convergence protocol (PDCP) layer belongs to the L2. ThePDCP layer provides a function of header compression function thatreduces unnecessary control information such that data being transmittedby employing IP packets, such as IPv4 or IPv6, can be efficientlytransmitted over a radio interface that has a relatively smallbandwidth. The header compression increases transmission efficiency inthe radio section by transmitting only necessary information in a headerof the data. In addition, the PDCP layer provides a function ofsecurity. The function of security includes ciphering which preventsinspection of third parties, and integrity protection which preventsdata manipulation of third parties.

A radio resource control (RRC) layer belongs to the L3. The RLC layer islocated at the lowest portion of the L3, and is only defined in thecontrol plane. The RRC layer takes a role of controlling a radioresource between the UE and the network. For this, the UE and thenetwork exchange an RRC message through the RRC layer. The RRC layercontrols logical channels, transport channels, and physical channels inrelation to the configuration, reconfiguration, and release of RBs. AnRB is a logical path provided by the L1 and L2 for data delivery betweenthe UE and the network. That is, the RB signifies a service provided theL2 for data transmission between the UE and E-UTRAN. The configurationof the RB implies a process for specifying a radio protocol layer andchannel properties to provide a particular service and for determiningrespective detailed parameters and operations. The RB is classified intotwo types, i.e., a signaling RB (SRB) and a data RB (DRB). The SRB isused as a path for transmitting an RRC message in the control plane. TheDRB is used as a path for transmitting user data in the user plane.

A Non-Access Stratum (NAS) layer placed over the RRC layer performsfunctions, such as session management and mobility management.

Referring to FIG. 2, the RLC and MAC layers (terminated in the eNB onthe network side) may perform functions such as scheduling, automaticrepeat request (ARQ), and hybrid automatic repeat request (HARQ). TheRRC layer (terminated in the eNB on the network side) may performfunctions such as broadcasting, paging, RRC connection management, RBcontrol, mobility functions, and UE measurement reporting andcontrolling. The NAS control protocol (terminated in the MME of gatewayon the network side) may perform functions such as a SAE bearermanagement, authentication, LTE_IDLE mobility handling, pagingorigination in LTE_IDLE, and security control for the signaling betweenthe gateway and UE.

Referring to FIG. 3, the RLC and MAC layers (terminated in the eNB onthe network side) may perform the same functions for the control plane.The PDCP layer (terminated in the eNB on the network side) may performthe user plane functions such as header compression, integrityprotection, and ciphering.

Hereinafter, An RRC state of a UE and RRC connection procedure aredescribed.

An RRC state indicates whether an RRC layer of the UE is logicallyconnected to an RRC layer of the E-UTRAN. The RRC state may be dividedinto two different states such as an RRC connected state and an RRC idlestate. When an RRC connection is established between the RRC layer ofthe UE and the RRC layer of the E-UTRAN, the UE is in RRC_CONNECTED, andotherwise the UE is in RRC_IDLE. Since the UE in RRC_CONNECTED has theRRC connection established with the E-UTRAN, the E-UTRAN may recognizethe existence of the UE in RRC_CONNECTED and may effectively control theUE. Meanwhile, the UE in RRC_IDLE may not be recognized by the E-UTRAN,and a CN manages the UE in unit of a TA which is a larger area than acell. That is, only the existence of the UE in RRC_IDLE is recognized inunit of a large area, and the UE must transition to RRC_CONNECTED toreceive a typical mobile communication service such as voice or datacommunication.

In RRC_IDLE state, the UE may receive broadcasts of system informationand paging information while the UE specifies a discontinuous reception(DRX) configured by NAS, and the UE has been allocated an identification(ID) which uniquely identifies the UE in a tracking area and may performpublic land mobile network (PLMN) selection and cell re-selection. Also,in RRC_IDLE state, no RRC context is stored in the eNB.

In RRC_CONNECTED state, the UE has an E-UTRAN RRC connection and acontext in the E-UTRAN, such that transmitting and/or receiving datato/from the eNB becomes possible. Also, the UE can report channelquality information and feedback information to the eNB. InRRC_CONNECTED state, the E-UTRAN knows the cell to which the UE belongs.Therefore, the network can transmit and/or receive data to/from UE, thenetwork can control mobility (handover and inter-radio accesstechnologies (RAT) cell change order to GSM EDGE radio access network(GERAN) with network assisted cell change (NACC)) of the UE, and thenetwork can perform cell measurements for a neighboring cell.

In RRC_IDLE state, the UE specifies the paging DRX cycle. Specifically,the UE monitors a paging signal at a specific paging occasion of everyUE specific paging DRX cycle. The paging occasion is a time intervalduring which a paging signal is transmitted. The UE has its own pagingoccasion.

A paging message is transmitted over all cells belonging to the sametracking area. If the UE moves from one TA to another TA, the UE willsend a tracking area update (TAU) message to the network to update itslocation.

When the user initially powers on the UE, the UE first searches for aproper cell and then remains in RRC_IDLE in the cell. When there is aneed to establish an RRC connection, the UE which remains in RRC_IDLEestablishes the RRC connection with the RRC of the E-UTRAN through anRRC connection procedure and then may transition to RRC_CONNECTED. TheUE which remains in RRC_IDLE may need to establish the RRC connectionwith the E-UTRAN when uplink data transmission is necessary due to auser's call attempt or the like or when there is a need to transmit aresponse message upon receiving a paging message from the E-UTRAN.

To manage mobility of the UE in the NAS layer, two states are defined,i.e., an EPS mobility management-REGISTERED (EMM-REGISTERED) state andan EMM-DEREGISTERED state. These two states apply to the UE and the MME.Initially, the UE is in the EMM-DEREGISTERED state. To access a network,the UE performs a process of registering to the network through aninitial attach procedure. If the attach procedure is successfullyperformed, the UE and the MME enter the EMM-REGISTERED state.

To manage a signaling connection between the UE and the EPC, two statesare defined, i.e., an EPS connection management (ECM)-IDLE state and anECM-CONNECTED state. These two states apply to the UE and the MME. Whenthe UE in the ECM-IDLE state establishes an RRC connection with theE-UTRAN, the UE enters the ECM-CONNECTED state. When the MME in theECM-IDLE state establishes an S1 connection with the E-UTRAN, the MMEenters the ECM-CONNECTED state. When the UE is in the ECM-IDLE state,the E-UTRAN does not have context information of the UE. Therefore, theUE in the ECM-IDLE state performs a UE-based mobility related proceduresuch as cell selection or reselection without having to receive acommand of the network. On the other hand, when the UE is in theECM-CONNECTED state, mobility of the UE is managed by the command of thenetwork. If a location of the UE in the ECM-IDLE state becomes differentfrom a location known to the network, the UE reports the location of theUE to the network through a tracking area update procedure.

FIG. 4 shows a procedure in which UE that is initially powered onexperiences a cell selection process, registers it with a network, andthen performs cell reselection if necessary.

Referring to FIG. 4, the UE selects Radio Access Technology (RAT) inwhich the UE communicates with a Public Land Mobile Network (PLMN), thatis, a network from which the UE is provided with service (S410).Information about the PLMN and the RAT may be selected by the user ofthe UE, and the information stored in a Universal Subscriber IdentityModule (USIM) may be used.

The UE selects a cell that has the greatest value and that belongs tocells having measured BS and signal intensity or quality greater than aspecific value (cell selection) (S420). In this case, the UE that ispowered off performs cell selection, which may be called initial cellselection. A cell selection procedure is described later in detail.After the cell selection, the UE receives system informationperiodically by the BS. The specific value refers to a value that isdefined in a system in order for the quality of a physical signal indata transmission/reception to be guaranteed. Accordingly, the specificvalue may differ depending on applied RAT.

If network registration is necessary, the UE performs a networkregistration procedure (S430). The UE registers its information (e.g.,an IMSI) with the network in order to receive service (e.g., paging)from the network. The UE does not register it with a network whenever itselects a cell, but registers it with a network when information aboutthe network (e.g., a Tracking Area Identity (TAD) included in systeminformation is different from information about the network that isknown to the UE.

The UE performs cell reselection based on a service environment providedby the cell or the environment of the UE (S440). If the value of theintensity or quality of a signal measured based on a BS from which theUE is provided with service is lower than that measured based on a BS ofa neighboring cell, the UE selects a cell that belongs to other cellsand that provides better signal characteristics than the cell of the BSthat is accessed by the UE. This process is called cell reselectiondifferently from the initial cell selection of the No. 2 process. Inthis case, temporal restriction conditions are placed in order for acell to be frequently reselected in response to a change of signalcharacteristic. A cell reselection procedure is described later indetail.

FIG. 5 shows an RRC connection establishment procedure.

The UE sends an RRC connection request message that requests RRCconnection to a network (S510). The network sends an RRC connectionestablishment message as a response to the RRC connection request(S520). After receiving the RRC connection establishment message, the UEenters RRC connected mode.

The UE sends an RRC connection establishment complete message used tocheck the successful completion of the RRC connection to the network(S530).

FIG. 6 shows an RRC connection reconfiguration procedure.

An RRC connection reconfiguration is used to modify RRC connection. Thisis used to establish/modify/release RBs, perform handover, and setup/modify/release measurements.

A network sends an RRC connection reconfiguration message for modifyingRRC connection to UE (S610). As a response to the RRC connectionreconfiguration message, the UE sends an RRC connection reconfigurationcomplete message used to check the successful completion of the RRCconnection reconfiguration to the network (S620).

The following is a detailed description of a procedure of selecting acell by a UE.

When power is turned-on or the UE is located in a cell, the UE performsprocedures for receiving a service by selecting/reselecting a suitablequality cell.

A UE in an RRC idle state should prepare to receive a service throughthe cell by always selecting a suitable quality cell. For example, a UEwhere power is turned-on just before should select the suitable qualitycell to be registered in a network. If the UE in an RRC connection stateenters in an RRC idle state, the UE should selects a cell for stay inthe RRC idle state. In this way, a procedure of selecting a cellsatisfying a certain condition by the UE in order to be in a serviceidle state such as the RRC idle state refers to cell selection. Sincethe cell selection is performed in a state that a cell in the RRC idlestate is not currently determined, it is important to select the cell asrapid as possible. Accordingly, if the cell provides a wireless signalquality of a predetermined level or greater, although the cell does notprovide the best wireless signal quality, the cell may be selectedduring a cell selection procedure of the UE.

Hereinafter, a method and a procedure of selecting a cell by a UE in a3GPP LTE is described.

A cell selection process is basically divided into two types.

The first is an initial cell selection process. In this process, UE doesnot have preliminary information about a wireless channel. Accordingly,the UE searches for all wireless channels in order to find out a propercell. The UE searches for the strongest cell in each channel.Thereafter, if the UE has only to search for a suitable cell thatsatisfies a cell selection criterion, the UE selects the correspondingcell.

Next, the UE may select the cell using stored information or usinginformation broadcasted by the cell. Accordingly, cell selection may befast compared to an initial cell selection process. If the UE has onlyto search for a cell that satisfies the cell selection criterion, the UEselects the corresponding cell. If a suitable cell that satisfies thecell selection criterion is not retrieved though such a process, the UEperforms an initial cell selection process.

After the UE selects a specific cell through the cell selection process,the intensity or quality of a signal between the UE and a BS may bechanged due to a change in the mobility or wireless environment of theUE. Accordingly, if the quality of the selected cell is deteriorated,the UE may select another cell that provides better quality. If a cellis reselected as described above, the UE selects a cell that providesbetter signal quality than the currently selected cell. Such a processis called cell reselection. In general, a basic object of the cellreselection process is to select a cell that provides UE with the bestquality from a viewpoint of the quality of a radio signal.

In addition to the viewpoint of the quality of a radio signal, a networkmay determine priority corresponding to each frequency, and may informthe UE of the determined priorities. The UE that has received thepriorities preferentially takes into consideration the priorities in acell reselection process compared to a radio signal quality criterion.

As described above, there is a method of selecting or reselecting a cellaccording to the signal characteristics of a wireless environment. Inselecting a cell for reselection when a cell is reselected, thefollowing cell reselection methods may be present according to the RATand frequency characteristics of the cell.

-   -   Intra-frequency cell reselection: UE reselects a cell having the        same center frequency as that of RAT, such as a cell on which        the UE camps on.    -   Inter-frequency cell reselection: UE reselects a cell having a        different center frequency from that of RAT, such as a cell on        which the UE camps on.    -   Inter-RAT cell reselection: UE reselects a cell that uses RAT        different from RAT on which the UE camps.

The principle of a cell reselection process is as follows.

First, UE measures the quality of a serving cell and neighbor cells forcell reselection.

Second, cell reselection is performed based on a cell reselectioncriterion. The cell reselection criterion has the followingcharacteristics in relation to the measurements of a serving cell andneighbor cells.

Intra-frequency cell reselection is basically based on ranking. Rankingis a task for defining a criterion value for evaluating cell reselectionand numbering cells using criterion values according to the size of thecriterion values. A cell having the best criterion is commonly calledthe best-ranked cell. The cell criterion value is based on the value ofa corresponding cell measured by UE, and may be a value to which afrequency offset or cell offset has been applied, if necessary.

Inter-frequency cell reselection is based on frequency priority providedby a network. UE attempts to camp on a frequency having the highestfrequency priority. A network may provide frequency priority that willbe applied by UEs within a cell in common through broadcastingsignaling, or may provide frequency-specific priority to each UE throughUE-dedicated signaling. A cell reselection priority provided throughbroadcast signaling may refer to a common priority. A cell reselectionpriority for each UE set by a network may refer to a dedicated priority.If receiving the dedicated priority, the UE may receive a valid timeassociated with the dedicated priority together. If receiving thededicated priority, the UE starts a validity timer set as the receivedvalid time together therewith. While the valid timer is operated, the UEapplies the dedicated priority in the RRC idle mode. If the valid timeris expired, the UE discards the dedicated priority and again applies thecommon priority.

For the inter-frequency cell reselection, a network may provide UE witha parameter (e.g., a frequency-specific offset) used in cell reselectionfor each frequency.

For the intra-frequency cell reselection or the inter-frequency cellreselection, a network may provide UE with a Neighboring Cell List (NCL)used in cell reselection. The NCL includes a cell-specific parameter(e.g., a cell-specific offset) used in cell reselection.

For the intra-frequency or inter-frequency cell reselection, a networkmay provide UE with a cell reselection black list used in cellreselection. The UE does not perform cell reselection on a cell includedin the black list.

Ranking performed in a cell reselection evaluation process is describedbelow.

A ranking criterion used to apply priority to a cell is defined as inEquation 1.R _(S) =Q _(meas,s) +Q _(hyst) ,R _(n) =Q _(meas,n) −Q_(offset)  [Equation 1]

In this case, Rs is the ranking criterion of a serving cell, Rn is theranking criterion of a neighbor cell, Qmeas,s is the quality value ofthe serving cell measured by UE, Qmeas,n is the quality value of theneighbor cell measured by UE, Qhyst is the hysteresis value for ranking,and Qoffset is an offset between the two cells.

In Intra-frequency, if UE receives an offset “Qoffsets,n” between aserving cell and a neighbor cell, Qoffset=Qoffsets,n. If UE does notQoffsets,n, Qoffset=0.

In Inter-frequency, if UE receives an offset “Qoffsets,n” for acorresponding cell, Qoffset=Qoffsets,n+Qfrequency. If UE does notreceive “Qoffsets,n”, Qoffset=Qfrequency.

If the ranking criterion Rs of a serving cell and the ranking criterionRn of a neighbor cell are changed in a similar state, ranking priorityis frequency changed as a result of the change, and UE may alternatelyreselect the twos. Qhyst is a parameter that gives hysteresis to cellreselection so that UE is prevented from to alternately reselecting twocells.

UE measures RS of a serving cell and Rn of a neighbor cell according tothe above equation, considers a cell having the greatest rankingcriterion value to be the best-ranked cell, and reselects the cell. If areselected cell is not a suitable cell, UE excludes a correspondingfrequency or a corresponding cell from the subject of cell reselection.

FIG. 7 shows an RRC connection re-establishment procedure.

Referring to FIG. 7, UE stops using all the radio bearers that have beenconfigured other than a Signaling Radio Bearer (SRB) #0, and initializesa variety of kinds of sublayers of an Access Stratum (AS) (S710).Furthermore, the UE configures each sublayer and the PHY layer as adefault configuration. In this procedure, the UE maintains the RRCconnection state.

The UE performs a cell selection procedure for performing an RRCconnection reconfiguration procedure (S720). The cell selectionprocedure of the RRC connection re-establishment procedure may beperformed in the same manner as the cell selection procedure that isperformed by the UE in the RRC idle state, although the UE maintains theRRC connection state.

After performing the cell selection procedure, the UE determines whetheror not a corresponding cell is a suitable cell by checking the systeminformation of the corresponding cell (S730). If the selected cell isdetermined to be a suitable E-UTRAN cell, the UE sends an RRC connectionre-establishment request message to the corresponding cell (S740).

Meanwhile, if the selected cell is determined to be a cell that uses RATdifferent from that of the E-UTRAN through the cell selection procedurefor performing the RRC connection re-establishment procedure, the UEstops the RRC connection re-establishment procedure and enters the RRCidle state (S750).

The UE may be implemented to finish checking whether the selected cellis a suitable cell through the cell selection procedure and thereception of the system information of the selected cell. To this end,the UE may drive a timer when the RRC connection re-establishmentprocedure is started. The timer may be stopped if it is determined thatthe UE has selected a suitable cell. If the timer expires, the UE mayconsider that the RRC connection re-establishment procedure has failed,and may enter the RRC idle state. Such a timer is hereinafter called anRLF timer. In LTE spec TS 36.331, a timer named “T311” may be used as anRLF timer. The UE may obtain the set value of the timer from the systeminformation of the serving cell.

If an RRC connection re-establishment request message is received fromthe UE and the request is accepted, a cell sends an RRC connectionre-establishment message to the UE.

The UE that has received the RRC connection re-establishment messagefrom the cell reconfigures a PDCP sublayer and an RLC sublayer with anSRB1. Furthermore, the UE calculates various key values related tosecurity setting, and reconfigures a PDCP sublayer responsible forsecurity as the newly calculated security key values. Accordingly, theSRB 1 between the UE and the cell is open, and the UE and the cell mayexchange RRC control messages. The UE completes the restart of the SRB1,and sends an RRC connection re-establishment complete message indicativeof that the RRC connection re-establishment procedure has been completedto the cell (S760).

In contrast, if the RRC connection re-establishment request message isreceived from the UE and the request is not accepted, the cell sends anRRC connection re-establishment reject message to the UE.

If the RRC connection re-establishment procedure is successfullyperformed, the cell and the UE perform an RRC connection reconfigurationprocedure. Accordingly, the UE recovers the state prior to the executionof the RRC connection re-establishment procedure, and the continuity ofservice is guaranteed to the upmost.

Hereinafter, machine type communication (MTC) will be described.

FIG. 8 shows an example of MTC.

MTC refers to information exchange between MTC UEs 810 via a BS 820without involving human interactions or information exchanges between anMTC UE 810 and an MTC server 830 via the BS. Services provided throughMTC are differentiated from existing communication services requiringhuman intervention, and MTC provides a wide range of services, such astracking, metering, payment, medical services, remote control, and thelike. More specifically, services provided through MTC may includereading a meter, measuring a water level, utilizing a surveillancecamera, reporting the inventory of a vending machine, and the like. Datacommunication-oriented low-cost/low-specification UEs that provide theseservices are referred to as an MTC UE or low complexity-type UE forconvenience. A BS may determine whether a UE is an MTC UE based on thecapability of the UE. In the present specification, an MTC UE, alow-complexity UE, a low-cost UE, and a UE Category 0 UE may be usedwith the same meaning, and a normal UE may be used to refer to a UEother than the listed UEs.

The MTC server 830 is an entity communicating with the MTC UE 810. TheMTC server 830 runs an MTC application and provides an MTC-specificservice to an MTC device. The MTC UE 810 is a wireless device thatprovides MTC communication and may be fixed or mobile.

Since an MTC UE has a small amount of data to transmit and isoccasionally involved in uplink/downlink data transmission/reception, itis effective to reduce the cost of the UE and to decrease batteryconsumption thereof according to a low data transmission rate. The MTCUE is characterized by low mobility and thus has a hardly changingchannel environment.

The MTC UE does not require a high-performance function and generallyuses a small amount of data. The concept of UE Category 0 is introducedin order to manufacture a low-cost MTC UE. A UE category is a generalnumber used in the 3GPP to indicate how much data a UE can process in acommunication modem. Table 1 shows 3GPP UE categories.

TABLE 1 UE Category DL speed UL speed 0  1 Mbps  1 Mbps 1  10 Mbps  5Mbps 2  50 Mbps 25 Mbps 3 100 Mbps 50 Mbps 4 150 Mbps 50 Mbps 5 300 Mbps75 Mbps 6 300 Mbps 50 Mbps 7 300 Mbps 100 Mbps  8  3 Gbps 1.5 Gbps  9450 Mbps 50 Mbps 10 450 Mbps 100 Mbps  11 600 Mbps 50 Mbps 12 600 Mbps100 Mbps  13 400 Mbps 50 Mbps

A UE Category 0 UE is allowed to process only 1 Mbps, making it possibleto manufacture a modem without much effort and high costs, and may useonly one antenna. Also, the UE Category 0 UE is allowed to performtransmission or reception only in a specified time, rather thansimultaneously performing transmission and reception, and thus mayoperate in FDD in the same manner as in TDD. In addition, unlike inexisting TDD, a sufficient switching time of about 1 ms may be assignedfor a period of transition between transmission and reception, therebyremarkably reducing costs for hardware components, particularly in viewof a modem and RF, overall.

MTC UEs may be installed not only in buildings and factories but also incoverage-limited places, for example, a basement. For instance, about20% of MTC UEs supporting an MTC service, such as smart metering, may beinstalled in a poor ‘deep indoor’ environment, such as a basement. Thus,for successful MTC data transmission, it is necessary to increase thecoverage of an MTC UE by about 20 dB as compared with the coverage of aconventional normal UE. Considering this situation, various coverageenhancement techniques are currently under discussion, such as arepetitive transmission method for an MTC UE by each channel/signal.

FIG. 9 shows an example of cell coverage enhancement for an MTC device.

As described above, various coverage enhancement techniques, such as arepetitive transmission method for an MTC UE by each channel/signal,have recently been under discussion.

According to a location of a UE in a cell and signal quality of the UEin the cell, the coverage extension technique may be required not onlyfor an MTC UE but also for a normal UE. In general, a repetitivetransmission method may be used as the coverage extension technique. Thenumber of repetitions required for successful transmission/reception maydiffer depending on a scenario and UE capability. For example, in theextended coverage (SNR=−14.3 dB), the number of repetitions performed on328-bit SIB by an MTC UE of Rel-13 may be about 150. In addition, it isexpected that the similar number of repetitions is also required in caseof paging.

A time required for successful transmission/reception may differdepending on the required number of repetitions. This may have an effecton all timer values of the standard document. In other words, a timeduration needs to be increased when a greater number of repetitions arerequired. On the contrary, a short time duration may be sufficient whena small number of repetitions are required. For example, if the UEattempts to establish an RRC connection, since a time fortransmitting/receiving signals/data differs depending on the coverageextension level (hereinafter, referred to as a ‘CE level’), the requiredtime may differ depending on the CE level.

In order to solve the aforementioned problem, the present inventionproposes a method in which a UE applies a value corresponding to a CElevel on the basis of the CE level, and an apparatus supporting themethod. For example, the value corresponding to the CE level may be atimer value, a window size, a maximum counter value, or the like.According to an embodiment of the present invention, the UE may includethree steps, i.e., a step of receiving a list including one or morevalues (e.g., a timer value, a window size, a maximum counter value, oran offset value) corresponding to one or more CE levels (first step), astep of determining the CE level (second step), and a step of applying avalue (e.g., a timer value, a window size, or a maximum counter value)corresponding to the determined CE level among the values included inthe list (third step). Hereinafter, each step will be described indetail.

1. First Step

(1) The UE may receive a list including one or more values correspondingto one or more CE levels through broadcast signaling. Additionally, theUE may receive the list including the one or more values correspondingto the one or more CE levels through dedicated signaling. The one ormore values may be one or more timer values, one or more window sizes,or one or more maximum counter values. The UE may be in an RRC_IDLEstate.

The one or more values may be provided by each CE level. For example, ifit is assumed that the CE level is defined from 0 to 3, the UE mayreceive from a network a 0th timer value corresponding to a CE level 0,a 1^(st) timer value corresponding to a CE level 1, a 2^(nd) timer valuecorresponding to a CE level 2, and a 3^(rd) timer value corresponding toa CE level 3. In addition, the UE may receive from the network a 0^(th)window size corresponding to the CE level 0, a 1^(st) window sizecorresponding to the CE level 1, a 2^(nd) window size corresponding tothe CE level 2, and a 3rd window size corresponding to the CE level 3.In addition, the UE may receive from the network a 0th maximum countervalue corresponding to the CE level 0, a 1^(st) maximum counter valuecorresponding to the CE level 1, a 2^(nd) maximum counter valuecorresponding to the CE level 2, and a 3^(rd) maximum counter valuecorresponding to the CE level 3. Although it is assumed in theembodiment of the present invention that the CE level can be set from 0to 3, this merely means that one or more levels can be set, and thetechnical scope of the present invention is not limited thereto. Amethod of determining the CE level by the UE is described in detail inthe second step. The higher the CE level, the longer the timer value,the greater the window size, and the greater the maximum counter value.

The one or more values (e.g., the timer value, the window size, or themaximum counter value) may be an RRC layer timer value, an RRC layerwindow size, or an RRC layer maximum counter value. For example, thevalue may be T300, T303, T305, T306, connEstFailCount, or a timer valueused by the UE to declare a failure in SIB acquisition. For example, inthe RRC connection establishment procedure, the higher the CE level ofthe UE, the longer the expiration time of T300.

The one or move values (e.g., the timer value, the window size, or thecounter value) may be a MAC layer timer value, a MAC layer window size,or a MAC layer maximum counter value. For example, it may bepreambleTransMax, mac-ContentionResolutionTimer, orra-ResponseWindowSize. For example, in the random access procedure, thehigher the CE level of the UE, the greater the maximum number ofpreambles to be transmitted (preambleTransMax). For example, in therandom access procedure, the higher the CE level of the UE, the greaterthe random access response window size (ra-ResponseWindowSize). Forexample, in the random access procedure, the higher the CE level of theUE, the longer the expiration time of the contention resolution timer(mac-ContentionResolutionTimer).

(2) Alternatively, the UE may receive a different offset value relatedto the CE level through broadcast signaling. The UE may also receive thedifferent offset value related to the CE level through dedicatedsignaling. The offset value may differ for each of the timer value, thewindow size, and the maximum counter value.

The UE may manipulate a specific value by using the received offsetvalue. The specific value may be any one of the timer value, the windowsize, and the maximum counter value. The manipulation may be performedby multiplication, addition, subtraction, and/or division. Themanipulated value may be different from each other depending on the CElevel of the UE. For example, the UE may increase a timer value in sucha manner that the higher the CE level, the greater the offset to beadded or multiplied. The UE may also increase the existing timer valuein such a manner that the higher the CE level, the smaller the offset tobe subtracted or divided.

(3) A broadcast message (e.g., SIB) may be classified into two types ofSIB.

A first type of the broadcast message is a common broadcast message forall UEs which use a different CE level. A second type is a separatebroadcast message for each CE UE. The UE may be required to receive thecommon broadcast message and a broadcast message related to the CE levelof the UE. The common broadcast message may be transmitted with amaximum CE level (the maximum number of repetitions/resources).

A different broadcast message (e.g., SIB) may be defined for each CElevel to provide information related to each CE level. The differentbroadcast message may be transmitted with different time/frequencyresources. In addition, each broadcast message corresponding to each CElevel may be transmitted with a repetition/resource amount correspondingto the CE level.

The different broadcast message (e.g., SIB) may be used to provide thetimer value, the window size, or the maximum counter value for each CElevel. For example, SIB20a may be used for a timer value, window size,or maximum counter value of a CE level 0, SIB20b may be used for a timervalue, window size, or maximum counter value of a CE level 1, and SIB20cmay be used for a timer value, window size, or maximum counter value fora CE level 2.

2. Second Step

The UE may determine a CE level. The UE may determine the CE level ofthe UE for transmission/reception in a specific cell in the followingmanner. Each threshold may be provided by a serving cell.

(1) RSRP/RSRQ-based CE level determination: The UE may determine a CElevel of a cell by comparing a measured RSRP/RSRQ result and a pre-setthreshold.

In order for the UE to determine the CE level in a specific cell, anetwork may set an RSRP/RSRQ threshold for one or more CE levels. Forexample, the network may signal a 0th RSRP/RSRQ threshold for a CE level0, a 1^(st) RSRP/RSRQ threshold for a CE level 1, a 2^(nd) RSRP/RSRQthreshold for a CE level 2, and a 3^(rd) RSRP/RSRQ threshold for a CElevel 3. The level 0 implies that there is no coverage extension formeasurement.

While performing measurement of a serving cell and a neighboring cell,the UE may determine the CE level by comparing a threshold which is setby the network and an RSRP/RSRQ result which is measured by the UE. Ifthe measurement result is higher than the 0th RSRP/RSRQ threshold, theUE may determine the CE level as 0. If the measurement result is lowerthan the 0th RSRP/RSRQ threshold and higher than the Pt RSRP/RSRQthreshold, the UE may determine the CE level as 1. If the measurementresult is lower than the Pt RSRP/RSRQ threshold and higher than the2^(nd) RSRP/RSRQ threshold, the UE may determine the CE level as 2.Likewise, if the measurement result is lower than the 2^(nd) RSRP/RSRQthreshold and higher than the 3^(rd) RSRP/RSRQ threshold, the UE maydetermine the CE level as 3.

(2) PSS (Primary Synchronization Signal)/SSS(Secondary SynchronizationSignal)-based CE level determination: The UE may determine a CE level ofa cell by comparing a time for acquiring PSS/SS and a pre-set threshold.

In order for the UE to determine the CE level in a specific cell, anetwork may set an RSRP/RSRQ threshold for one or more CE levels. Forexample, the network may signal a 0th time threshold for a CE level 0, aPt time threshold for a CE level 1, a 2^(nd) time threshold for a CElevel 2, and a 3^(rd) time threshold for a CE level 3. The level 0implies that there is no coverage extension for measurement.

While performing measurement of a serving cell and a neighboring cell,the UE may determine a CE level by comparing a time threshold which isset by the network and a time for acquiring PSS/SSS. If the time foracquiring the PSS/SSS is shorter than the 0^(th) time threshold, the UEmay determine the CE level as 0. If the time for acquiring the PSS/SSSis longer than the 0^(th) time threshold and shorter than the 1^(st)time threshold, the UE may determine the CE level as 1. If the time foracquiring the PSS/SSS is longer than the Pt time threshold and shorterthan the 2^(nd) time threshold, the UE may determine the CE level as 2.If the time for acquiring the PSS/SSS is longer than the 2^(nd) timethreshold and shorter than the 3^(rd) time threshold, the UE maydetermine the CE level as 3.

(3) Downlink message-based CE level determination: The UE may determinea CE level of a cell by comparing the number of repetitions required tosuccessfully receive a certain downlink message and a pre-set threshold.

(4) Uplink message-based CE level determination: The UE may determine aCE level of a cell by comparing the number of repetitions required tosuccessfully transmit a certain uplink message and a pre-set threshold.

Although it is assumed in the embodiment of the present invention thatthe CE level can be set from 0 to 3, this merely means that one or morelevels can be set, and the technical scope of the present invention isnot limited thereto.

3. Third Step

(1) The UE may apply a value corresponding to the CE level determined inthe second step among values included in the list received in the firststep. The value corresponding to the determined CE level may be a timervalue corresponding to the determined CE level, a window sizecorresponding to the determined CE level, or a maximum counter valuecorresponding to the determined CE level. That is, the valuecorresponding to the determined CE level may be determined when a MAClayer, RLC layer, or RRC layer operation starts/restarts. For example,the timer value, window size, or maximum counter value corresponding tothe determined CE level may be determined when the UE transmits an RRCconnection request, when an access is prohibited during an RRCconnection establishment is performed for mobile originatingcall/signaling/CS fallback, when mac-ContentionResolutionTimer starts,when mac-ContentionResolutionTimer restarts, or when a preambletransmission counter is set to 1.

While operating (e.g., a timer is running, a counter value is not aninitial value (i.e., the value is increased/decreased), a time is in themiddle of a window), even if the CE level is changed, a valuecorresponding to the CE level determined when the MAC layer, RLC layer,or RRC layer operation starts may not be changed.

When a timer stops and/or expires, the value corresponding to thedetermined CE level may be re-evaluated on the basis of a current CElevel of the UE. For example, when the counter stops, the timer value,the window size, or the maximum counter value may be re-evaluated on thebasis of the current CE level of the UE.

A timer and/or a counter may start when initial transmission/receptionstarts during repetition. Alternatively, the timer and/or the countermay start when transmission/reception ends during repetition.

The method described through the first step to the third step may alsobe applied to a UE in an RRC_CONNECTED state. A method improved from themethod applied in a UE in the RRC_IDLE state may be applied to the UE inthe RRC_CONNECTED state. If the CE level is changed while the UE is inthe RRC_CONNECTED state, the UE may notify the network that the CE levelis changed. The notification may be transmitted to the network after theUE changes the CE level. The CE level may be determined in theaforementioned second step. The notification may include at least anyone of the changed CE level, a difference between a previous CE leveland the changed CE level, and the number of repetitions (resources)further required to transmit uplink data/signal or downlink data/signalin comparison with the previous CE level. Upon receiving thenotification, the network may reconfigure the timer value, the windowsize, the maximum counter value, or the like.

FIG. 10 shows a method of considering a CE level of a UE in acontention-based random access procedure according to an embodiment ofthe present invention.

(1) Per-CE Level Parameter Configuration and CE Level Determination(S1000)

Before starting the random access procedure, it is assumed that thefollowing information can be used for a CE UE.

-   -   prach-ConfigIndex: a set of available PRACH resources related to        each CE level supported in a serving cell for transmission of a        random access preamble.    -   preambleMappingInfoList: a set of random access preambles        available in each group, and a group of random access preambles.        A preamble included in the random access preamble for each CE        level is calculated, if exists, from parameters firstPreamble        and lastPreamble.    -   RSRP-ThresholdsPrachInfoList: a PRACH resource selection        criterion based on RSRP measurement for each CE level supported        in a serving cell.    -   maxNumPreambleAttemptCE: the maximum number of preambles to be        transmitted for each CE level supported in a serving cell.    -   numRepetitionPerPreambleAttempt: the number of repetitions        required for a preamble transmission attempt for each CE level        supported in a serving cell.    -   ra-ResponseWindowSize: a random access response window size for        each CE level supported in a serving cell.    -   mac-ContentionResolutionTimer: a contention resolution timer for        each CE level supported in a serving cell.    -   preambleTransMax-CE: the maximum number of preambles to be        transmitted.

In case of the CE UE, the CE level of the UE may be determined beforethe random access procedure starts. For example, if the measured RSRP isless than an RSRP of the CE level 3, it may be regarded that a MACentity is at the CE level 3. Otherwise, if the measured RSRP is lessthan an RSRP of the CE level 2, it may be regarded that the MAC entityis at the CE level 2. Otherwise, if the measured RSRP is less than anRSRP of the CE level 1, it may be regarded that the MAC entity is at theCE level 1. Otherwise, it may be regarded that the MAC entity is at theCE level 0. The RSRP of the CE level 3, the RSRP of the CE level 2, andthe RSRP of the CE level 1 may be included inRSRP-ThresholdsPrachInfoList.

(2) First Message Transmission (S1010)

The UE may randomly select one random access preamble from a set ofrandom access preambles indicated through system information or handovercommands, and may select a physical RACH (PRACH) resource capable oftransmitting the random access preamble. The UE may transmit theselected preamble by using the selected PRACH resource.

The maximum number of preambles to be transmitted (preambleTransMax) mayindicate the maximum number of preambles which can be transmitted untilthe UE starts a specific operation while performing the random accessoperation. The maximum number of preambles to be transmitted for each CElevel (maxNumPreambleAttemptCE) may indicate, for each CE level, themaximum number of preambles which can be transmitted until the UE startsthe specific operation while performing the random access operation.

The specific operation may be RRC connection re-establishment or thelike. A BS may set preambleTransMax to a proper value to preventpreamble transmission from being infinitely repeated. Alternatively, theBS may set maxNumPreambleAttemptCE to a proper value to prevent preambletransmission from being infinitely repeated.

The UE may receive from the network a list including one or more values‘preambleTransMax’ corresponding to one or more CE levels. For example,if it is assumed that the CE level is set to 0 to 3, the UE may receive,from the network, preambleTransMax corresponding to the CE level 0,preambleTransMax corresponding to the CE level 1, preambleTransMaxcorresponding to the CE level 2, and preambleTransMax corresponding tothe CE level 3. The higher the CE level, the greater thepreambleTransMax. That is, the maximum number of preambles to betransmitted may be increased in proportion to an increase in the CElevel.

Alternatively, the UE may receive from the network a list including oneor more values ‘maxNumPreambleAttemptCE’ corresponding to one or more CElevels. For example, if it is assumed that the CE level is set to 0 to3, the UE may receive, from the network, maxNumPreambleAttemptCEcorresponding to the CE level 0, maxNumPreambleAttemptCE correspondingto the CE level 1, maxNumPreambleAttemptCE corresponding to the CE level2, and maxNumPreambleAttemptCE corresponding to the CE level 3. Thehigher the CE level, the greater the maxNumPreambleAttemptCE.

Alternatively, the UE may receive an offset from the network. The UE mayuse the offset value to adjust preambleTransMax ormaxNumPreambleAttemptCE. The adjustment may be performed bymultiplication, addition, subtraction, and/or division. The adjustedvalue may be different from each other depending on the CE level of theUE.

(3) Second Message Reception (S1020)

The UE may receive random access response information from the BS. Thatis, after transmitting a random access preamble (S1010), the UE mayattempt to receive its random attach response within a random accessresponse window size (ra-ResponseWindowSize) indicated by the BS throughsystem information or handover commands. Thereafter, a PDSCH may bereceived through corresponding RA-RNTI information. Accordingly, the UEmay receive a UL grant, a temporary C-RNTI, a timing advance command(TAC), or the like.

The random access response window size (ra-ResponseWindowSize) is amaximum time duration in which the UE which has transmitted the preamblewaits to receive the random access response message. If the UE fails toreceive a valid random access response message until the random accessresponse window ends, the UE may perform preamble retransmission. Thatis, if the UE fails to receive the valid random access response messageuntil the random access response window ends, the UE may perform thestep S1010 again.

The UE may receive from the network a list including one or more values‘ra-ResponseWindowSize’ corresponding to one or more CE levels. Forexample, if it is assumed that the CE level is set to 0 to 3, the UE mayreceive, from the network, ra-ResponseWindowSize corresponding to the CElevel 0, ra-ResponseWindowSize corresponding to the CE level 1,ra-ResponseWindowSize corresponding to the CE level 2, andra-ResponseWindowSize corresponding to the CE level 3. The higher the CElevel, the greater the ra-ResponseWindowSize. That is, a maximum timeduration in which the UE waits to receive the random access responsemessage may be increased in proportion to an increase in the CE level.

Alternatively, the UE may receive an offset from the network. The UE mayuse the offset value to adjust ra-ResponseWindowSize. The adjustment maybe performed by multiplication, addition, subtraction, and/or division.The adjusted value may be different from each other depending on the CElevel of the UE.

(4) Third Message Transmission (S1030)

In a case where the UE receives a random access response which is validfor the UE, each piece of information included in the random accessresponse may be processed. That is, the UE may apply TAC, and may storea temporary C-RNTI. In addition, data (i.e., a third message) may betransmitted to the BS by using a UL grant. The third message mustinclude an identifier of the UE. In the contention-based random accessprocedure, the BS cannot determine which UEs perform the random accessprocedure because the UE must be identified for future contentionresolution.

Two methods are present as a method of including an identifier of theUE. In a first method, if the UE has a valid cell identifier which hasalready assigned in a corresponding cell before the random accessprocedure, the UE transmits its cell identifier through an uplinktransmission signal corresponding to the UL grant. On the other hand, ifthe valid cell identifier is not assigned before the random accessprocedure, the UE performs transmission by including its uniqueidentifier (e.g., an S-TMSI or a random ID). In general, the uniqueidentifier may be longer than a cell identifier. The UE may start acontention resolution timer (mac-ContentionResolutionTimer) if datacorresponding to the UL grant is transmitted.

(5) Fourth Message Reception (S1040)

The UE may transmit data including its identifier through a UL grantincluded in a random access response, and thereafter may wait for anindication of the BS for contention resolution. That is, PDCCH receptionmay be attempted to receive a specific message. There are two methodsfor receiving the PDCCH. If the UE has a valid cell identifier which hasalready assigned in a corresponding cell before the random accessprocedure and thus transmits its cell identifier through an uplinktransmission signal corresponding to the UL grant, PDCCH reception maybe attempted by using its cell identifier. Otherwise, if the UE does nothave the valid cell identifier assigned before the random accessprocedure and thus the UE transmits its unique identifier, PDCCHreception may be attempted by using a temporary C-RNTI included in arandom access response.

Thereafter, in the former case, if the PDCCH including its cellidentifier is received before the contention resolution timer expires,the UE may determine that the random access procedure is normallyperformed and thus may end the random access procedure. If the PDCCHincluding its cell identifier is not received before the contentionresolution timer expires, the UE may determine that it fails in thecontention, and thus may perform the random attach procedure again ormay notify a failure occurrence to an upper layer.

In the latter case, if the PDCCH is received through the temporaryC-RNTI before the contention resolution timer expires, data delivered bya PDSCH indicated by the PDDCH is confirmed. If its unique identifier isincluded in content of the data, the UE may determine that the randomaccess procedure is normally performed and thus may end the randomaccess procedure.

The UE may receive from the network a list including one or more values‘mac-ContentionResolutionTimer’ corresponding to one or more CE levels.For example, if it is assumed that the CE level is set to 0 to 3, the UEmay receive, from the network, mac-ContentionResolutionTimercorresponding to the CE level 0, mac-ContentionResolutionTimercorresponding to the CE level 1, mac-ContentionResolutionTimercorresponding to the CE level 2, and mac-ContentionResolutionTimercorresponding to the CE level 3. The higher the CE level, the greaterthe mac-ContentionResolutionTimer. That is, the higher the CE level, thelonger the time of the contention resolution timer.

Alternatively, the UE may receive an offset from the network. The UE mayuse the offset value to adjust mac-ContentionResolutionTimer. Theadjustment may be performed by multiplication, addition, subtraction,and/or division. The adjusted value may be different from each otherdepending on the CE level of the UE.

Although it is assumed in the example of FIG. 10 that the CE level canbe set from 0 to 3, this merely means that one or more levels can beset, and the technical scope of the present invention is not limitedthereto.

FIG. 11 shows a method of considering a CE level of a UE in an RRCconnection establishment procedure according to an embodiment of thepresent invention.

Referring to FIG. 11, it is assumed that a width of an arrow correspondsto the number of repetitions for successful transmission/reception, anda high CE level requires the great number of repetitions for successfultransmission/reception.

A BS may broadcast a list including one or more timer values (e.g.,T300) corresponding to one or more CE levels (S1100). The list may bebroadcast through system information. For example, the list may includea timer value corresponding to a CE level 0, a timer value correspondingto a CE level 1, a timer value corresponding to a CE level 2, and atimer value corresponding to a CE level 3.

A first UE may be triggered to establish an RRC connection (S1110).

A second UE may be triggered to establish an RRC connection (S1120).

The first UE of the CE level 3 and the second UE of the CE level 1 maytransmit an RRC connection establishment message to a network (S1130,S1140). Since the CE level of the first UE is higher than the CE levelof the second UE, the number of repetitions of the RRC connectionrequest message of the first UE may be greater than the number ofrepetitions of the RRC connection request message of the second UE.

The first UE of the CE level 3 may apply a timer value corresponding tothe CE level 3 among timer values included in the list, and a timer towhich a corresponding value is applied may run (S1150).

The second UE of the CE level 1 may apply a timer value corresponding tothe CE level 1 among the timer values included in the list, and a timerto which a corresponding value is applied may run (S1160).

Since the CE level of the first UE is higher than the CE level of thesecond UE, a timer running time of the first UE may be longer than atimer running time of the second UE.

FIG. 12 shows a method of considering a CE level of a UE in an RRCconnection establishment procedure according to an embodiment of thepresent invention.

Referring to FIG. 12, it is assumed that a width of an arrow correspondsto the number of repetitions for successful transmission/reception, anda high CE level requires the great number of repetitions for successfultransmission/reception.

A BS may broadcast a timer value (e.g., T300) and one or more offsetscorresponding to one or more CE levels (S1200). For example, the offsetmay include a 0th offset corresponding to a CE level 0, a first offsetcorresponding to a CE level 1, a second offset corresponding to a CElevel 2, and a third offset corresponding to a CE level 3.

A first UE may be triggered to establish an RRC connection (S1210).

A second UE may be triggered to establish an RRC connection (S1220).

The first UE of the CE level 3 and the second UE of the CE level 1 maytransmit an RRC connection establishment message to a network (S1230,S1240). Since the CE level of the first UE is higher than the CE levelof the second UE, the number of repetitions of the RRC connectionrequest message of the first UE may be greater than the number ofrepetitions of the RRC connection request message of the second UE.

The first UE of the CE level 3 may manipulate a timer value by using anoffset corresponding to the CE level 3 among the offsets. Thereafter,the manipulated timer may run (S1250).

The second UE of the CE level 1 may manipulate a timer value by using anoffset corresponding to the CE level 1 among the offsets. Thereafter,the manipulated timer may run (S1260). The manipulation may be performedby multiplication, addition, subtraction, and/or division. Themanipulated value may be different from each other depending on the CElevel of the UE.

Since the CE level of the first UE is higher than the CE level of thesecond UE, a timer running time of the first UE manipulated by theoffset may be longer than a timer running time of the second UEmanipulated by the offset.

FIG. 13 is a flowchart illustrating a method of applying a valuecorresponding to a CE level on the basis of the CE level of a UEaccording to an embodiment of the present invention.

The UE may receive a list including one or more values corresponding toone or more CE levels from a network (S1310).

The list may include a parameter used in a random access procedure. Theparameter used in the random access procedure may include at least anyone of mac-ContentionResolutionTimer, ra-ResponseWindowSize, andpreambleTransMax.

The list may include one or more timer values corresponding to the oneor more CE levels. The timer value may be T300. The timer value may beT303. The timer value may be T305. The timer value may be T306. Thetimer value may be a timer value used by the UE to declare a failure inSIB acquisition. The timer value may be mac-ContentionResolutionTimer.The higher the CE level, the longer the timer value.

The list may include one or more window sizes corresponding to the oneor more CE levels. The window size may be ra-ResponseWindowSize. Thehigher the CE level, the greater the window size.

The list may include one or more maximum counter values corresponding tothe one or more CE levels. The maximum counter value may beconnEstFailCount. The maximum counter value may be preambleTransMax. Themaximum counter value may be maxNumPreambleAttemptCE.

The list may be broadcast from a BS.

The UE may be in an RRC_IDLE state.

The UE may determine the CE level (S1320).

The CE level may be determined by comparing a measured RSRP/RSRQ resultand a pre-set threshold. The CE level may be determined by comparing atime for acquiring PSS/SSS and the pre-set threshold. The CE level maybe determined by comparing the number of repetitions required tosuccessfully receive a certain downlink message and the pre-setthreshold. The CE level may be determined by comparing the number ofrepetitions required to successfully transmit a certain uplink messageand the pre-set threshold.

The UE may apply a value corresponding to the determine CE level amongvalues included in the list (S1330).

The UE may perform a cell attach procedure, a cell re-attach procedure,a random access procedure, or data transmission/reception by using avalue corresponding to the applied CE level.

FIG. 14 is a flowchart illustrating a method of applying a valuecorresponding to a CE level on the basis of the CE level of a UEaccording to an embodiment of the present invention.

The UE may receive a specific value and one or more offset valuescorresponding to one or more CE levels from a network (S1410).

The specific value may be any one of a timer value, a window size, and amaximum counter value. The offset value may differ for each of the timervalue, the window size, or the maximum counter value. The offset valuemay differ depending on the CE level of the UE.

The UE may determine the CE level (S1420).

The CE level may be determined by comparing a measured RSRP/RSRQ resultand a pre-set threshold. The CE level may be determined by comparing atime for acquiring PSS/SSS and the pre-set threshold. The CE level maybe determined by comparing the number of repetitions required tosuccessfully receive a certain downlink message and the pre-setthreshold. The CE level may be determined by comparing the number ofrepetitions required to successfully transmit a certain uplink messageand the pre-set threshold.

The UE may manipulate the specific value by using an offset valuecorresponding to the determined CE level (S1430).

The specific timer value may be any one of the timer value, the windowsize, and the maximum counter value. The manipulation of the specificvalue may be performed by multiplication, addition, subtraction, ordivision.

The UE may apply the manipulated specific value (S1440).

The manipulated specific value may differ from each other according tothe CE level. The UE may perform a cell attach procedure, a cellre-attach procedure, a random access procedure, or datatransmission/reception by using the manipulated specific value.

FIG. 15 is a block diagram illustrating a wireless communication systemaccording to the embodiment of the present invention.

A BS 1500 includes a processor 1501, a memory 1502 and a transceiver1503. The memory 1502 is connected to the processor 1501, and storesvarious information for driving the processor 1501. The transceiver 1503is connected to the processor 1501, and transmits and/or receives radiosignals. The processor 1501 implements proposed functions, processesand/or methods. In the above embodiment, an operation of the basestation may be implemented by the processor 1501.

A UE 1510 includes a processor 1511, a memory 1512 and a transceiver1513. The memory 1512 is connected to the processor 1511, and storesvarious information for driving the processor 1511. The transceiver 1513is connected to the processor 1511, and transmits and/or receives radiosignals. The processor 1511 implements proposed functions, processesand/or methods. In the above embodiment, an operation of the UE may beimplemented by the processor 1511.

The processor may include an application-specific integrated circuit(ASIC), a separate chipset, a logic circuit, and/or a data processingunit. The memory may include a read-only memory (ROM), a random accessmemory (RAM), a flash memory, a memory card, a storage medium, and/orother equivalent storage devices. The transceiver may include abase-band circuit for processing a wireless signal. When the embodimentis implemented in software, the aforementioned methods can beimplemented with a module (i.e., process, function, etc.) for performingthe aforementioned functions. The module may be stored in the memory andmay be performed by the processor. The memory may be located inside oroutside the processor, and may be coupled to the processor by usingvarious well-known means.

Various methods based on the present specification have been describedby referring to drawings and reference numerals given in the drawings onthe basis of the aforementioned examples. Although each method describesmultiple steps or blocks in a specific order for convenience ofexplanation, the invention disclosed in the claims is not limited to theorder of the steps or blocks, and each step or block can be implementedin a different order, or can be performed simultaneously with othersteps or blocks. In addition, those ordinarily skilled in the art canknow that the invention is not limited to each of the steps or blocks,and at least one different step can be added or deleted withoutdeparting from the scope and spirit of the invention.

The aforementioned embodiment includes various examples. It should benoted that those ordinarily skilled in the art know that all possiblecombinations of examples cannot be explained, and also know that variouscombinations can be derived from the technique of the presentspecification. Therefore, the protection scope of the invention shouldbe determined by combining various examples described in the detailedexplanation, without departing from the scope of the following claims.

What is claimed is:
 1. A method performed by a wireless device in awireless communication system, the method comprising: receiving aplurality of thresholds from a network; receiving, from the network, arandom access channel (RACH) information for each coverage enhancement(CE) level, wherein the RACH information includes (1) a random accessresponse window size, and (2) a timer for contention resolution;performing at least one measurement for a cell; determining, among aplurality of CE levels, a CE level based on the plurality of thresholdsand results of the performed at least one measurement for the cell,wherein the CE level is determined as a CE level 0, based on that theresults of the performed at least one measurement for the cell is notless than all of the plurality of thresholds; selecting, among the RACHinformation, (1) a random access response window size corresponding tothe CE level 0, and (2) a timer for contention resolution correspondingto the CE level 0; and performing a random access procedure with thenetwork based on (1) the selected random access response window size,and (2) the selected timer for contention resolution, wherein the randomaccess to the network comprises receiving, from the network, a randomaccess response based on the random access response window sizecorresponding to the CE level
 0. 2. The method of claim 1, wherein theplurality of thresholds are received via system information.
 3. Themethod of claim 1, wherein the at least one measurement comprises areference signal received power (RSRP) measurement for the cell.
 4. Themethod of claim 3, wherein the at least one measurement furthercomprises a reference signal received quality (RSRQ) measurement for thecell.
 5. The method of claim 1, wherein as the plurality of CE levelsare configured with a higher CE level, the longer a timer value is inthe timer information.
 6. The method of claim 1, wherein the randomaccess to the network comprises, receiving, from the network, acontention resolution based on the timer for contention resolutioncorresponding to the CE level
 0. 7. A wireless device in a wirelesscommunication system, the wireless device comprising: a memory; atransceiver; and a processor operatively coupled to the memory and thetransceiver, wherein the processor is configured to: control thetransceiver to receive a plurality of thresholds from a network; controlthe transceiver to receive, from the network, a random access channel(RACH) information for each coverage enhancement (CE) level, wherein theRACH information includes (1) a random access response window size, and(2) a timer for contention resolution; perform at least one measurementfor a cell; determine, among a plurality of coverage enhancement (CE)levels, a CE level based on the plurality of thresholds and results ofthe performed at least one measurement for the cell, wherein the CElevel is determined as a CE level 0, based on that the results of theperformed at least one measurement for the cell is not less than all ofthe plurality of thresholds; select, among the RACH information, (1) arandom access response window size corresponding to the CE level 0, and(2) a timer for contention resolution corresponding to the CE level 0;and perform a random access procedure with the network based on (1) theselected random access response window size, and (2) the selected timerfor contention resolution, wherein the random access to the networkcomprises receiving, from the network, a random access response based onthe random access response window size corresponding to the CE level 0.8. The wireless device of claim 7, wherein the plurality of thresholdsare received via system information.